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In practical applications, it is typical for different types of sheathings (referred to as dissimilar) to be connected at both flanges of the stud (lipped channel-section) in cold-formed steel (CFS) panelised construction (e.g. one-side has interior sheathing and the other exterior sheathing). However, limited studies are available on the axial behaviour of CFS studs with different combinations of sheathings present at both-flanges of a stud. This novel experimental study investigates the structural behaviour of fourteen (14) CFS panels with sheathing on one-side only and different sheathing on both flanges of the wall panel using combinations of seven (7) different sheathing boards [fibre-cement boards (FCB) (8 mm/10 mm/12 mm thick); calcium silicate boards (CSB) (12 mm thick); and heavy duty FCB (6 mm/9 mm/12 mm thick)]. The ultimate axial strength, load-deformation behaviour and failure patterns are the parameters compared. Analytical/semi-analytical design methodologies namely; Rayleigh-Ritz (R-R) method, finite-strip method based on direct strength method (DSM) and differential equation of equilibrium method (DEEM) are validated based on the experiments. Limited studies are available to verify the efficacy of these methods to estimate the axial strength of CFS wall panels with dissimilar sheathing on both flanges. Results establish that DSM may be used efficiently rather than the R-R method and DEEM. [ABSTRACT FROM AUTHOR]

Two methods to predict the pushover response of a hybrid steel braced frame that features concentric and eccentric connections are presented. The proposed hybrid frame configuration is intended for cold-formed steel (CFS) building structures and plays a dual role by providing gravity and lateral load resistance. The hybrid system features CFS columns for resisting gravity loads, tension only CFS straps connected concentrically to hollow structural steel (HSS) chords for resisting lateral loads, and prestressing strands connected eccentrically to the same HSS chords for further enhancing lateral load capacity. The first pushover response prediction method employs a nonlinear finite element modeling protocol that features only beam and truss elements. This method is presented as an alternative to three-dimensional (3D) nonlinear finite element models, which require considerable modeling effort due to the multitude of the components included in the hybrid system, and the variety of interactions that would need to be defined. The second method includes closed form equations that allow the definition of the pushover curves using manual calculations and is appropriate for preliminary analysis. Formulations for predicting the initial in-plane system stiffness, and secondary stiffness are presented. Similarly, formulations for predicting the load to cause the first and second yield as well as ultimate lateral load capacity are provided. A closed form equation is presented to obtain the ultimate lateral displacement, which completes the definition of the pushover curve. The validation of the proposed pushover response prediction methods is conducted by first comparing responses from 3D nonlinear FEA to those obtained from the simplified FEA model. Similarly, predictions from the simplified FEA model are compared to those obtained from the closed form equations. Good agreements are noted in both cases. The influence of hybrid steel braced frame aspect ratio on system push over response is quantified. The contribution of each lateral load resisting element to lateral load capacity is presented as a function of aspect ratio. Finally, improvements in behavior and enhancements in lateral load capacity offered by the hybrid frame-wall compared to the traditional strapped wall system are demonstrated through monotonic pushover, cyclic pushover, and response history analysis. [ABSTRACT FROM AUTHOR]

The current paper presents an innovative form of the cold‐formed U‐shape steel encasing concrete composite beam (CUCB). The suggested CUCB consists of a cold‐formed U‐shaped steel encasing plain concrete beam which are connected to each other using continuous transversal threaded stud bolts. The experimental program consisted of eight beam specimens tested in the four‐point bending set‐up. One of them was a normal reinforced concrete beam and considered as a reference specimen while the remaining specimens were CUCB specimens without ordinary flexural and shear reinforcement. Four parameters were studied in this paper: (i) the thickness of the U‐shaped steel, (ii) the spacing between the stud bolts, (iii) the arrangement of the bolts, and (iv) the number of the bolt's rows. Results indicated an overall improvement in the load‐carrying capacity and stiffness of most CUCB specimens in comparison with the reference specimen. It was found that the using of three rows of bolts can significantly improve the ductility and toughness of the CUCB specimen in comparison with two rows of bolts. On the contrary, an increase in the bolt spacing entails a decrease in the CUCB specimens' toughness. [ABSTRACT FROM AUTHOR]

This study aims to develop optimized interaction equations for more efficient design of cold-formed steel (CFS) lipped channel beam-columns under combined compressive load and biaxial bending, aligned with the direct strength method (DSM). A comprehensive data set was first generated using detailed experimentally validated finite element (FE) models of over 500 CFS sections subjected to combined compression and uniaxial and biaxial bending moments while the effects of initial geometric imperfections and material nonlinearity were included. The compiled data set consisted of a range of key design variables, including cross-sectional geometry and element length, as well as combinations of compression and bending moments caused by various eccentricity levels in terms of direction and value. The results were subsequently utilized to evaluate the efficiency of the simplified interaction formula prescribed by the Australian/New Zealand Standard (AS/NZS-4600) and American Iron and Steel Institute (AISI-S100), as well as the extended DSM, in predicting the capacity of CFS lipped channel beam-column elements. It was demonstrated that, on average, using existing interaction equations may lead to a 32% error in the capacity predictions of CFS beam-column members. Following a reliability analysis, a new interaction expression was developed with optimized parameters using DSM nominal pure strength values. For the first time, different exponent parameters were proposed for minor- and major-axes bending, which resulted in a considerable improvement in the accuracy of the beam-column strength predictions compared to the existing methods. [ABSTRACT FROM AUTHOR]

Built-up back-to-back cold-formed steel (CFS) channel members (BBC members) are utilized as CFS compression members with enhanced load-bearing capacity in building structures. In this study, finite-element (FE) models of BBC compression members with pinned warping-fixed and pinned warping-free ends were established and verified using test results available in the literature. Using the developed FE models, detailed parametric studies were conducted to assess the behavior and capacity of slender BBC compression members with pinned warping-free ends, varying cross sections, and screw arrangements. The results were first compared with those of their individual (channel) members and BBC members with pinned warping-fixed ends. They were then used to evaluate the direct strength method (DSM) design rules in the CFS design standards used in North America and Australia/New Zealand. Finally, new reliable design rules based on the DSM equations and some analytical equations in the literature were proposed for the BBC compression members with pinned warping-free ends, together with suitable recommendations. This paper includes the main details of this study with a summary of its important findings and proposals. [ABSTRACT FROM AUTHOR]

A novel figure of merit based on the concept of signature curve for cold formed steel (CFS) cross sections is used to improve the structural member's overall behavior regardless of length and boundary conditions. The objective is defined as the area under the signature curve, plus a penalty function that ensures improved performance over standard sections at specified lengths. Charged system search (CSS), a meta-heuristic optimization algorithm, is used to search the design space. End-use and other geometrical constraints suggested by previous studies are considered to arrive at practical cross sections. This includes limiting the fold angles to minimize sharp corners in the optimized cross sections, which might result in residual stresses that diminish axial capacity. Such nonlinear constraints are also taken into account using penalty functions to facilitate integration with the heuristic optimization process. The proposed strategy is examined through a couple of illustrative examples and is shown to yield higher axial capacity at all points when combined with the proper penalization. The optimized cross sections are also analyzed in simple-simple and clamped-clamped boundary conditions showing improved axial capacity compared to the standard lipped-channel sections with the same coil width. [ABSTRACT FROM AUTHOR]

Cold-formed thick-walled steel members have a higher bearing capacity and wider applicability in the mid-rise buildings in comparison with the widely-used cold-formed thin-walled steel framing walls in low-rise buildings. To avoid the shortcomings of cold-forming effect, a structure with hinged or semi-rigid joint steel frame using cold-formed thick-walled steel and cold-formed thin-walled steel framing shear wall is one reasonable choices, and it will be very helpful to simplify the on-site assembling processes. In this paper, a cross-shaped joint with adjustable stiffness was proposed, and better seismic performance was investigated and confirmed by tests. By increasing the thickness of the web plates of the cross-shaped joint, the bearing capacity, stiffness, and ductility of the joint can be significantly improved, and the buckling deformation of the web plate will be reduced. Moreover, a strengthening stiffener, Type 2 proposed in the paper, has a significantly effect on the cross-shaped joint for seismic damage and intact specimens. Using ANSYS software and the SOLID185 element, a finite element model was established. With the increasing thickness of the end plate of the stiffener Type 2, both the stiffness and bearing capacity of the cross-shaped joint can be significantly increased. [ABSTRACT FROM AUTHOR]

Portal frames with built-up cold-formed cross-sections hold significant potential; however, there is a notable gap in the analysis of cross-section types and connections. In this study, an optimization algorithm was developed for the closed cross-sections of portal frame members. An optimization algorithm was tested against optimized open cold-formed cross-sections. The results indicated a portal frame volume up to 38% lower where members were assembled of optimal closed cross-sections when compared to frames with optimal open cross-sections. Parametric analysis was carried out, where two types of cross-sections were examined: Type A, with four web stiffeners bent inwards, and Type B, with four web stiffeners bent outwards. The optimization was conducted using a Genetic Algorithm in MATLAB R2022b. Portal frames with optimal Type B cross-sections had a volume that was up to 22% lower when compared to frames with optimal Type A cross-sections. Significant differences were noted between the optimal beam and column cross-sections, with the optimal column cross-section thickness being on average 74% greater, but the optimal beam cross-section height being on average 81% greater than those of the respective counterparts. In this article, a practical assembly solution for the connection of the frame members was proposed for the optimized novel closed cross-section types in portal frames. However, the strength and stiffness of these connections were not analyzed in this research. [ABSTRACT FROM AUTHOR]

Cold-formed steel (CFS) sections have become popular in construction due to several advantages over structural steel. However, research on the performance of galvanized iron (GI)-based CFS under high temperatures, especially regarding its flexural behavior, has been limited. This study extensively investigates how GI-based CFS beams with varying spans behave under elevated temperatures and subsequent cooling using air and water. This study examines the impact of temperature loading and compares the effectiveness of air- and water-cooling methods. Experimental results are validated and analyzed alongside findings from finite element modeling (FEM) using ABAQUS (2019_09_13-23.19.31) and the Direct Strength Method (DSM). Additionally, this study conducts a parametric investigation to assess how beam span influences flexural capacity. Among beams heated to the same temperature, those cooled with water show slightly lower load capacities compared to those cooled with air. The highest load capacity observed is 64.3 kN for the reference specimen, while the lowest is 26.2 kN for the specimen heated for 90 min and cooled with water, a 59.27% difference between them. Stiffness decreases as heating duration increases, with the reference section exhibiting significantly higher stiffness compared to the section heated for 90 min and cooled with water, with a 92.76% difference in stiffness. As heating duration increases, ductility also increases. Various failure modes are observed based on different heating and cooling conditions across different beam spans. This study provides insights into how GI-based CFS beams perform under temperature stress and different cooling scenarios, contributing valuable data for structural design and safety considerations in construction. [ABSTRACT FROM AUTHOR]

To improve the seismic behaviour of cold-formed steel (CFS) walls, a novel infilled CFS wall covered with different wall sheathings (gypsum wallboard, oriented strand board and fibre cement board) was assessed. Four full-scale specimens were tested under cyclic lateral loads to investigate the impacts of the wall sheathings on the seismic performance of the CFS wall. The failure process, failure mode, load–displacement curve, strength degradation, stiffness degradation, energy dissipation, deformation and strain variation of the walls were investigated. The failure modes of the walls were found to be failure of the connections between the CFS frame and the sheathing as well as crushing of the infill material. Compared with a specimen without sheathing, the peak load and lateral stiffness of the walls with sheathing were increased by 1.25–1.72 times, indicating that the sheathings played an important role in the lateral resistance of the wall. An analysis model and formulas for predicting wall lateral stiffness were developed. Comparisons between the calculations and experimental data showed that the proposed theoretical method was able to predict the lateral stiffness of the infilled CFS walls accurately. [ABSTRACT FROM AUTHOR]

This paper presents experimental studies to investigate the compressive and shear behaviors of cold-formed thin-walled steel-foam concrete composite walls. Three compressive walls and three shear walls were tested. The failure mode and load-displacement curve of the specimen were obtained from the compressive experiment. The compressive wall infilled with foam concrete mainly experienced distortion buckling of the end stud and local crushing failure of the concrete. The stud openings had a limited effect on the compressive bearing capacity of the composite wall. The failure mode and load-deformation curve were obtained in shear tests. The ductility index, shear stiffness, yield load, peak load, energy dissipation, and stiffness degradation were analyzed. The shear composite wall filled with foam concrete mainly occurred concrete crushing failure, local or distortional buckling failure of the end stud, and cracking failure of the calcium silicate board. The shear stiffness, shear capacity, ductility, and energy dissipation of the composite wall could be significantly improved after filling with foam concrete. [ABSTRACT FROM AUTHOR]

In this study, the structural performance of a new type of lightweight composite cold-formed steel and timber (CFST) flooring system has been investigated by conducting four-point bending tests on 13 specimens. A bare cold-formed steel system without timber sheathing was also tested to provide a benchmark response to which the strength and stiffness of the composite system were compared. This paper presents key findings on the flooring system's structural behavior and performance parameters, such as ultimate bending capacity, load-deflection response, load-slip response, and failure modes, by categorizing 13 specimens into four subgroups based on shear connector types and spacings. In the proposed composite CFST flooring system, 45-mm thick structural plywood panels were connected to the 2.4-mm thick cold-formed steel C-section joist using self-drilling screws, coach screws, and nuts and bolts. The performance of different types of shear connectors on the composite action is experimentally investigated and compared with the theoretical plastic section. Furthermore, the load-carrying capacity, effective bending stiffness, and deflection of composite CFST beams were computed theoretically using elastic theory and compared to experimental results, which showed good agreement. [ABSTRACT FROM AUTHOR]

To provide more suggestions for the anti‐fatigue design of cold‐formed steel, a series of high‐cycle fatigue tests are carried out on cold‐rolled steel sheets connected by self‐tapping screws and blind rivets in this paper. Subsequently, fatigue failure mode, fatigue strength, and fatigue damage are analyzed in detail. The test results show that all effective data points are below the S‐N curve of screws in the code. Meanwhile, the fatigue limit values of the fitted curves with 95% survival probability fall within the range of 0.3 to 0.67 times the specified value. Besides, the fatigue damage expansion rate of cold‐rolled steel sheets is less than the standard value. Through further discussion, it is noticed that metal grade has little influence on the fatigue performance, while thickness has a significantly positive influence on the shear resistance and fatigue performance. Moreover, the fatigue performance of the two connection types appears to be similar. Highlights: The base metal has little effect on the fatigue performance of cold‐rolled steel connections.Thickness raises the shear and fatigue performance of cold‐rolled steel connections.The fatigue performance of the two types of cold‐rolled steel connections is similar. [ABSTRACT FROM AUTHOR]

In the rapidly evolving field of sustainable construction, this study aims to address the critical need for advancement in the building industry, focusing on vital indicators like energy efficiency and cost-effectiveness, as well as improving occupant comfort. This research introduces a novel approach to support the choice of suitable structural systems for mass housing projects, with a case study on Iran's national housing scheme. This methodology involves a four-phase process, beginning with compiling a database from existing studies to outline primary and secondary indicators affecting structural system selection. It utilizes the fuzzy AHP method for criteria prioritization and the fuzzy TOPSIS technique for alternatives (LSF, 3DP, ICF, TRC, and RCCF). The study identified the light steel framing (LSF) system as the optimal choice for Iran's housing needs based on various criteria. Then, in the final phase, the study evaluates the seismic performance of cold-formed steel (CFS) frames with various sheathing panel types (OSB, DFP, CSP, and GWB) under monotonic loads, examining key seismic parameters across 38 frame setups. The findings reveal that LSF structures can effectively withstand seismic events within the elastic behavior range, suggesting that this construction approach is viable for enhancing mass housing production in Iran's construction sector. [ABSTRACT FROM AUTHOR]

Concrete-filled built-up cold-formed steel (CFS) columns offer enhanced load-carrying capacity, improved strength-to-weight ratios, and delayed buckling through providing internal resistance and stiffness due to the concrete infill. Integrating sustainable alternatives like self-compacting geopolymer concrete (SCGC) with low carbon emissions is increasingly favoured for addressing environmental concerns in construction. This review aims to explore the current knowledge regarding CFS built-up composite columns and the performance of SCGC within them. While research on geopolymer concrete-filled steel tubes (GPCFSTs) under various loads has demonstrated high strength and ductility, investigations into built-up sections remain limited. The literature suggests that geopolymer concrete's superior compressive strength, fire resistance, and minimal shrinkage render it highly compatible with steel tubular columns, providing robust load-bearing capacity and gradual post-ultimate strength, attributed to the confinement effect of the outer steel tubes, thereby preventing brittle failure. Additionally, in built-up sections, connector penetration depth and spacing, particularly at the ends, enhances structural performance through composite action in CFS structures. Consequently, understanding the importance of using a sustainable and superior infill like SCGC, the cross-sectional efficiency of CFS sections, and optimal shear connections in built-up CFS columns is crucial. Moreover, there is a potential for developing environmentally sustainable built-up CFS composite columns using SCGC cured at ambient temperatures as infill. [ABSTRACT FROM AUTHOR]

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A new structural typology of a Steel-Reinforced Wooden (SRW) purlin made of rectangular laminated wood and C-section type cold-formed steel is presented in this article. The steel C-section profile is fitted onto the wooden purlin so that both work together as a composite unit. Although the wooden sections are weaker and have a lower elastic modulus than the steel sections, the overall dimensions of the SRW purlins are no larger than the steel C-section purlin sizes. The SRW purlins also form lighter structures than either plain steel or wooden purlins and they therefore have lower CO2 emissions. In addition, lighter purlins reduce the load on the main structure, which in turn reduces the material needed for the main structure of the building. So, reinforcement of the wooden purlin with steel sections within certain areas notably improved performance when compared with ordinary single-material purlins. The use of the SRW purlins can, therefore, improve the overall sustainability of a building. The improvements were analyzed in terms of sustainability and lower weight, as a function of span length and design load. The behaviors of the single material purlins and the SRW purlin were also compared. Both material strength and deformation design criteria and their influence were studied using an analytical approach based on loading and span length. The simple, innovative, and reliable design procedure described in this study ensured compliance with all technical requirements. Moreover, the savings relating to material weight were evaluated, neutralizing the carbon footprint in all cases under analysis. [ABSTRACT FROM AUTHOR]

Cold-formed steel is being used as a viable substitute for traditional steel and building materials due to its performance, affordability, convenience, lightweight, and environmental friendliness. The major purpose of this current research is for a reaction to force-deformation at the connection level to be delivered, which is proper for typical cold-formed steel (CFS) screwed beam-column assembly CFS C-section, and to show the influence of the behavior of CFS under bending test. An inner plate, double angle plate, and self-drilling screws are used by a basic beam-column frame idealized CFS to join the beam-column. Fixed support was implemented at the column base, whereas the beam end had free support. A 0.75 mm cold-formed steel C-section with 80mm height and 30mm width was utilized in this study and assembled into an "I" and "box" configuration. 3d and 4d were used to compute screw spacing for self-drilling screws with 4 mm heads and 2 mm bodies. The first type was each angle plate (top and seat angle) screwed with eight screws, whereas the second involves four screws. The CFS section’s thinness led to the use of screw connections, which are essential to their ability to withstand connection failures, to anticipate the failure mode of the connection segment. Numerical simulation by ABAQUS Student Edition and analytical studies have been conducted by AS/NZS 4600:2018 to investigate the capacity of CFS under bending. Quantity and the arrangement of the screws determine the displacement ductility with tighter spacing enhancing performance and reinforcing global and local buckling resistance.